The invention relates to an adjustable cartridge case gauge especially for edgeless shoulder cartridges used for firearms, comprising a head portion adjacent to said shoulder and a foot portion adjacent to the bolt of a breech mechanism, the distance between said head portion and said foot portion may be adjusted in an infinitely variable manner.
For the manufacture, the fire test and the repair of firearms cartridges, space gauging devices are necessary by which the size of the cartridge space of the corresponding gun, for instance a pistol, may be measured and by which it can be checked whether or not the prescribed size is present.
U.S. Pat. No. 2,668,360 discloses a head space gauge for firearms by which the distance for the face of the bolt of a closed breech mechanism to the shoulder in the chamber of a barrel against which cartridges are seated can be defined. Although this known gauge is also adjustable in length and moreover the adjusted position thereof will not be changed upon the closing and opening the breech mechanism, this gauge needs a considerable number of spacer shims of different thickness which are to be positioned between the surfaces of a forward and a rearward section of the gauge for changing the measurement between the gauging surfaces.
The above construction is therefore cumbersome and rather expensive to manufacture.
According to U.S. Pat. No. 3,510,951 concerning a cartridge head space gauging device for rifle firing chambers measuring the space between a tapered forward shoulder of the firing chamber and the face of a breech block or bolt of a rifle in close condition is accomplished by joining a fore or front member shaped with an outer surface configuration including a tapered forward end which dimensionally conforms to the forward end of a cartridge shell for the chamber of a rifle and a rear member provided with an end face engageable by the breech block or bolt of the rifle with outer portions forwardly thereof having outer surfaces identical with corresponding surfaces of the cartridge shell. These two members are separated by a deformable ring to define a length greater than the length of a standard cartridge shell The whole device consisting of the above two members and the ting are placed in the firing chamber and thereafter removed therefrom and placed in a suitable gauging instrument to determine the exact dimension of the firing chamber. Thus, this gauging device is also rather expensive to manufacture and to use.
U.S. Pat. No. 2,553,704 concerns a head space gauge for firearms using a telescopic means consisting of two parts indicating the exact head space when introduced in the chamber of the rifle and the bolt is closed.
Although this device is rather simple to manufacture and use it is not suited for a great number of firing chambers in general but only for special configurated firing chambers provided with tapered shoulders the slope and length thereof correspond to the configuration of a conical portion of the head of the cylindrical plug of the gauge.
Moreover, U.S. Pat. No. 3,209,461 concerning an adjustable cartridge case gauge is also providing a rather simple and inexpensive device convenient to use, it needs, however, a great number of inserts adapted to the gauge body by employing threads. This construction does therefore not fulfil the requirements concerning a very precise measurement using less as possible elements.
In case of shoulder cartridges the cone-tool-head length of the cartridge, measured between the shoulder engaged by the cartridge and the bottom of the cartridge, called breech distance, is of special importance. Normally this kind of gauges consist of one piece. Thus, for each kind of cartridge gauges for minimum and maximum dimensions are necessary resulting in high costs because of the great number of the present cartridges. Moreover, it is rather cumbersome to find out by means of the above mentioned fixed gauges the real length of the cartridge chamber if no exactly suited gauge exists for that purpose.
As mentioned above adjustable gauges have already been proposed comprising two parts moveable with respect to one another so that these two parts may be slideably engaged and connected to one another to different lengths by means of friction. Using this kind of gauges the measuring operation should be such that at first the gauge is adjusted to a size greater than the nominal size and in such a condition introduced into the cartridge chamber. Thereafter the breech is closed. At the same time the gauge is adapted to the real dimensions. After the gauge will have been taken off the cartridge chamber its length may be determined. In practise, however, this construction is not satisfying.
To summarize the above discussed prior art the devices one can say that all known gauges are in so far disadvantageous as for each kind and size of cartridge at least one special gauge must be prepared and stored what is not only expensive but also cumbersome and requests space for keeping a greater number of gauges every time available.